The present invention relates to a process for the preparation of water-soluble salts of poly-.alpha.-hydroxyacrylic acid or its alkyl derivatives.
Various methods have already been proposed for synthesizing these polyelectrolytes which can be used as agents for sequestering metal ions and as builders in detergents as described in Belgian Patent No. 776,705 of Dec. 15, 1971 in the name of Solvay and Cie.
C. S. Marvell et al (J. Am. Chem. Soc., 1940, 62, pp. 3495-3498) have proposed a method of synthesis starting from methyl acrylate, which is a very expensive starting material. In Belgian Patent No. 786,464 of July 19, 1972, there is described a more economical process for preparing salts of poly-.alpha.-hydroxyacrylic acid, starting from acrylic acid. Although this process is more economical, it nevertheless requires several intermediate steps and the consumption of reagents is rather high.
German Patent Application DOS No. 2,061,584 of Dec. 15, 1970 in the name of HENKEL u. Co. aims to provide a process for synthesizing these polyelectrolytes by treating an .alpha.,.beta.-dihalogeno-propionic acid with an alkali and converting the product obtained into a water-soluble salt. This process also possesses the disadvantage of requiring rather large amounts of reagents, and especially of sodium hydroxide.